Three envelope package for sterile specimens

ABSTRACT

A three-envelope package for preserving tissue specimens or other sterile objects. A sterile tissue sample is sealed within an innermost envelope sterile inside and out. The innermost envelope is sealed within the sterile interior of an intermediate envelope equipped with a peel-back seal for subsequent opening. Both the inside and the outside of the intermediate envelope are sterile. The intermediate envelope is sealed within the sterile interior of an outermost envelope, made of foil or another substance impermeable to a storage medium, such as liquid nitrogen. The outermost envelope provides complete impermeability to liquid nitrogen, eliminating the possibility of nitrogen seepage through the peel-back seal of the intermediate envelope. When the envelope package is removed from storage, the intermediate envelope is removed from the outermost envelope and can be opened in an assumed non-sterile environment, without contaminating the innermost envelope or the tissue specimen therein.

This is a continuation of application Ser. No. 395,297 filed Aug. 17,1989, now U.S. Pat. No. 5,031,762, which is a continuation-in-part ofapplication Ser. No. 105,220 filed Oct. 7, 1987, abandoned.

TECHNICAL FIELD

The present invention relates in general to packaging for sterilespecimens, and more particularly relates to a package for storing asterile transplant specimen in a preserving medium and maintainingsterility when subsequently removing the specimens from the package.

BACKGROUND OF THE INVENTION

There are presently available various kinds of packaging for sterilespecimens. The sterile specimens may be biological, marine, oragricultural specimens stored for analysis in a laboratory. The sterilespecimen may also be human or animal tissue for use in transplants.

Human tissue transplant operations have become commonplace in recenttimes. The success of these transplant operations has created a highdemand for the human tissue. However, it is often difficult to findfresh donor tissue for immediate transplant to a recipient. Donor tissuemust match the recipient's tissue as closely as possible, to minimizethe risk of tissue rejection by the recipient's immune system, and forthat reason homografts are preferred; heart valves and blood vessels aretwo examples of human tissue currently used for human homografts. Thetissue is preferably preserved and stored for later implant so that asupply of tissue is on hand independently of immediate donoravailability.

Human and animal tissue is preferably cryopreserved for storage beyond afew hours. The tissue, after excision from the donor and suitabletreatment as known to those skilled in the art, is stored in a sterilepackage impermeable to bacteria and then frozen, after which the frozentissue is stored at a low temperature for relatively long-termpreservation. Because the low temperatures required for effectivecryopreservation are not attainable by economically-feasible mechanicalrefrigeration equipment, the packaged tissue specimens are stored byimmersion in liquid nitrogen to maintain the cryopreserved tissue viablethroughout storage. It is, therefore, important that the storage packagebe impermeable to liquid nitrogen. When a suitable recipient is foundfor the tissue, the storage package is removed from the liquid nitrogenstorage facility. The tissue is then thawed and removed from its storagepackage immediately before implant in the recipient.

The tissue must be kept sterile during removal from the storage packagebefore implanting in the recipient. This is not a trivial requirement,as the exterior surface of the storage package is nonsterile or ispresumed as such. The sterile packages known in the prior art areinadequate for storing cryopreserved human or animal tissue specimens,because these packages cannot insure the sterility of the specimen whenthe package is stored in an unsterile coolant medium such as liquidnitrogen. Packaging material impermeable to liquid nitrogen is wellknown, metallic foil being one example, but simply making the prior artpackaging out of material impermeable to liquid nitrogen does not solvethe problems of sterility. Because the outer surface of such an envelopeis unsterile, there is a risk of contamination of the specimen when theenvelope is cut open and the specimen is pulled out of the envelope.

Foil envelopes or pouches with a peel-back opening feature have beenproposed as a solution to the foregoing problem. A peel-back openingallows an envelope to be opened by pulling apart the two sides of theenvelope, so that the contents are exposed and can be removed withoutcontacting the outer surface of the envelope. However, the outer surfaceof any single-envelope package is always considered unsterile. A furtherproblem with a single envelope package is that an envelope with apeel-back opening feature is not impermeable to liquid nitrogen. Since asingle-envelope package for storing specimens in liquid nitrogen cannothave a peel-back opening, the envelope must be cut open to remove thespecimen. There is then a substantial risk that the specimen will makeactual physical contact with the unsterile outer surface or opening ofthe envelope and become contaminated.

Various double-envelope packages for storing sterile specimens have beenproposed. A typical double envelope package for storing specimens isalso inadequate for insuring sterility of a cryopreserved specimen. Atypical double envelope package is made of a sterile inner envelope thatcontains the specimen, and this inner envelope is stored in an outerenvelope impermeable to liquid nitrogen. When the outer envelope is cutopen and the inner envelope is removed, there is a substantial risk thatthe sterile outer surface of the inner envelope will become contaminatedfrom contact with the unsterile outer surface of the outer envelope.Likewise, when the sterile specimen is removed from the inner envelope,there is some risk that the specimen will be contaminated by thepresumed-unsterile outer surface of the inner envelope. Making the innerbag with a peel-back opening in a two-envelope package does not solvethe problem of sterility. The tissue specimen is stored in a liquidmedium in the inner envelope. If the inner envelope is opened by peelingoff part of the inner envelope, the liquid will pour uncontrollably outof the inner envelope, and contact the outside surface of the innerenvelope, causing inconvenience and a further risk of contamination tothe specimen.

Therefore, there is a need for a package for storing sterile tissuespecimens in a coolant medium such as liquid nitrogen and maintainingthe sterility of the tissue specimen when the specimen is removed fromthe packaging.

SUMMARY OF THE INVENTION

The present invention solves the above-described problems in the priorart by providing a three-envelope package for storing sterile specimens.Generally described, the present invention is comprised of threeenvelopes: an inner envelope, an intermediate envelope, and an outerenvelope. The inner envelope is made of a material completelyimpermeable to bacteria, and the sterile tissue specimen is stored inthe inner envelope. The inner envelope is sterile inside and out, when atissue specimen is deposited therein.

The inner envelope is then stored in the intermediate envelope, alsomade of a material impermeable to bacteria. The intermediate envelope isalso sterilized inside and out, when the inner envelope is storedtherein. In the preferred embodiment of this invention, the intermediateenvelope is made with a peel-back flap that allows the intermediateenvelope to be opened by pulling the two sides of the envelope apart,thereby exposing the contents of the inner envelope.

The intermediate envelope is stored in the outer envelope. The outerenvelope is made of a material completely impermeable both to liquidnitrogen and bacteria. The outer envelope is sterile on the inside whenstored but is not sterile on the outside when stored, because the outersurface of the outer envelope contacts an unsterile universe includingthe cryogenic coolant medium.

The novel construction of the present invention insures the sterility ofthe tissue specimen as the specimen is removed from the package. Whenthe tissue specimen is needed, the package containing the sterilespecimen is removed from the coolant medium and the tissue specimen isthawed. The outer envelope is then cut open, and the intermediateenvelope is pulled from the outer envelope and the outer envelope isdiscarded. It is possible that the outer surface of the intermediateenvelope is contaminated by contact with the unsterile cut edge of theouter envelope as the intermediate envelope is removed, and in any casethe outer surface of the intermediate envelope is treated as if it werecontaminated. Although the outer surface of the intermediate envelope ispresumed unsterile, the inner envelope can remain sterile while beingremoved from the intermediate envelope. The peel-back flap of theintermediate envelope is pulled, thereby pulling apart the two sides ofthe intermediate envelope and exposing the inner envelope. Next, theinner envelope is lifted from the intermediate envelope by a sterileinstrument so that the inner envelope does not contact the peeled-backunsterile outer surface of the intermediate envelope. The outer surfaceof the inner envelope thus remains sterile after the inner envelope isremoved from the intermediate envelope. The intermediate envelope isthen discarded and the sterile inner envelope is introduced to a sterileenvironment. The tissue specimen is there removed from the innerenvelope with no risk of contamination from contact with the outersurface of the intermediate envelope.

Therefore, it is an object of the present invention to provide animproved package for cryopreserving a tissue specimen until the tissuespecimen can be implanted in a recipient.

It is a further object of the present invention to provide a package forstoring sterile tissue specimens in a cooling medium such as liquidnitrogen.

It is a another object of the invention to provide a package for storingtissue specimens whereby the tissue specimen can be removed therefrom ina sterile condition.

Other objects, features and advantages will become apparent from readingthe following specifications in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a pictorial view, partially broken away for illustrativepurposes, showing a package according to a preferred embodiment of thepresent invention.

FIG. 2 is a plan view, also partially broken away, showing the packageof FIG. 1.

FIG. 3 is a pictorial view illustrating the stages of opening thepackage shown in FIGS. 1 and 2.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

Referring first to FIGS. 1 and 2, there is shown generally at 10 anenvelope package including three individual envelopes or pouches. Theseenvelopes are the outermost envelope 12, an intermediate envelope 14contained immediately within the outermost envelope, and an innermostenvelope 16 received within the intermediate envelope. The tissuespecimen (generally at 17) is contained within only the innermostenvelope 16 in the present embodiment of the invention, and it will beunderstood that the innermost envelope may also contain a suitableliquid medium (17a) for preserving the viability of the tissue specimen.Furthermore, although the disclosed embodiment is discussed as a sterilemeans for storing and substantially utilizing a cryopreserved specimenof human or animal tissue, that specific application is not intended tolimit the utility of the present invention.

The outermost envelope 12 provides the dual functions of isolating itssterile interior from bacteria, and of providing an impermeable barrierto the cryogenic atmosphere (irrespective of sterility) in which theenvelope is kept. Liquid nitrogen comprises the particular cryogenicatmosphere of concern for the envelope package 10 of the preferredembodiment, and so the outermost envelope 12 must be impervious toliquid nitrogen. A metallic foil, such as aluminum foil or the like, isa preferred material for fabricating the outermost envelope 12.

The outermost envelope is fabricated from two foil panels 12a and a 12b(FIG. 2) of equal dimensions, overlaying each other and enclosing theintermediate envelope 14. The interior of the outermost envelope 12 issterilized before receiving the intermediate envelope 14. The peripheraledges 18 of the outermost envelope 12 are then welded shut along thealigned 19 by heat sealing or another appropriate sealing techniquewhich makes the outermost envelope impervious to bacteria and topenetration by the liquid nitrogen in which the envelope package 10 isthen placed.

The innermost envelope 16 receives the sterile tissue specimen 17 and,typically, a liquid medium (17a) which bathes the tissue specimen. Theinnermost envelope 16, while in the envelope package 10, is not exposedto liquid nitrogen, nor to an unsterile condition, and so the innermostenvelope is preferably a polyester bag of sufficient size to contain thetissue specimen and any supporting liquid medium. The innermost envelopeis sterile inside and out, and is sealed shut at one end 16a by heatsealing or the like after the tissue specimen and any liquid medium arein place within the innermost envelope.

The intermediate envelope 14 is preferably of peel-back construction, tofacilitate subsequent opening of that envelope without subjecting theinnermost envelope 16 contained within the intermediate envelope, topossible contamination on the outer surface of the intermediateenvelope. However, the intermediate envelope 14 is protected by theoutermost envelope 12 against exposure to the liquid nitrogen storagemedium, and so the possibility of liquid nitrogen seeping through thepeel-back seal of the intermediate envelope is eliminated.

Details of the intermediate envelope 14 are best seen in FIG. 3. Theintermediate envelope 14 is of two-piece construction, including a lowerlayer 24 sandwiched beneath an upper layer 25. The upper and lowerlayers are preferably rectangular sheets of thin flexible material suchas foil or polyester, as is known to those skilled in the art.Confronting peripheral portions of the facing surfaces on the layers 24and 25 are sealed together as at the seal line 28, and this seal linepreferably extends on three sides of the intermediate envelope 14. Theseal 28 is a peel-back seal of known construction, in which theconfronting surfaces of the lower layer 24 and the upper layer 25 aretack-sealed together by heating or the like, forming an airtight sealimpervious to the passage of bacteria or other contaminants. The fourthside 29 of the intermediate envelope 14 is welded together in arelatively permanent seal, and the fourth side also is impervious tobacteria or other contaminants. The seal 28 and fourth side 29 thusdefine an interior region 26 within the intermediate envelope 14, andthis interior region is of sufficient dimension to receive theaforementioned innermost envelope 16 as illustrated in FIG. 4. Both theinside and outside of the intermediate envelope 14 are sterilized.

A preferred construction of the intermediate envelope 14 has one of thelayers 24 and 25, for example, the upper layer 25, made of a transparentpolyester sheet, and the other layer made of foil, the two layers beingheat-sealed or otherwise interconnected along three sides to form thepeel-back seal 28. The peel-back seal 28 preferably follows a diagonalpath 30 across at least one corner of the intermediate envelope 14,leaving the outermost corner 31 unsealed to facilitate grasping andopening the peel-back seal. The use of dissimilar materials, such asfoil and vinyl, for the layers 24 and 25 facilitates forming a seal 28having the desired peel-back characteristics necessary for opening theenvelope package as described below. Inasmuch as the outermost envelope12 is a barrier to liquid nitrogen, the intermediate envelope 14 isnever subjected to liquid nitrogen and the permeability of peel-backseals to liquid nitrogen is not a problem with the present envelopepackage 10.

The package described herein further serves to protect the cryogenicallypreserved transplantable tissue contained in the innermost envelope. Tofacilitate the cryogenic preservation of the transplantable tissuecontained in the package described herein, the package should be made ofmaterial which is suitable for exposure to extremely low temperatures,e.g., -196 degrees C. to elevated temperatures, e.g., +37 degrees C.,such as are observed and utilized in the preparation of cryogenicallypreserved tissue for transplant into a patient in need of suchtreatment. The envelope material should withstand wide, rapid, extremefreeze-thaw temperature changes without cracking, be chemically inertand enhance or preserve the tissue to improve tissue viability upontransplant. Table I shows a list of commonly available materials andtheir brittleness temperatures.

                  TABLE I                                                         ______________________________________                                        LIST OF COMMONLY USED PLASTICS                                                               Brittleness                                                    Resin          Temp (°F./°C.                                    ______________________________________                                        LDPE*          -148/-100                                                      HDPE*          -148/-100                                                      XLPE           -180/-118                                                      PP             32/0                                                           PA             -40/-40                                                        PMP            68/20                                                          PS             -148/-100                                                      PVC            -22/-30                                                        ACL            --                                                             NYL*           32/0                                                           PC             -211/-135                                                      PSF            -148/-100                                                      FEP*           -454/-270                                                      ETFE/ECTFE     -157/-105                                                      PFA            -454/-270                                                      PUR            -94/-70                                                        LEGEND                                                                        LDPE: Low-density polyethylene                                                HDPE: High-density polyethylene                                               XLPE: Cross-linked, high-density polyethylene                                 PP: Polypropylene                                                             PA: Polyallomer                                                               PMP: Polymethylpentene                                                        PMMA: Polymethyl methacrylate                                                 PVC: Polyvinyl chloride                                                       ACL: Acetal (polyoxymethylene)                                                NYL: Nylon (polyamide)                                                        PC: Polycarbonate                                                             PSF: Polysulfone                                                              TFE: Teflon TFE (tetrafluoroethylene)                                         FEP: Teflon FEP (fluorinated ethylene polypropylene)                          ETFE: Tefzel ETFE (ethylene-tetrafluoroethylene)                              ECTFE: Halar ECTFE (ethylene-chlorotrifluoroethylene                          copolymer)                                                                    PFA: Teflon PFA (perfluoroalkoyl)                                             PUR: Polyurethane                                                             PVDF: Polyvinylidene fluoride                                                 PS: Polystyrene                                                               ______________________________________                                         *Materials tested in this study                                          

At temperatures near or below the brittleness temperature, thesematerials become fragile. An example of material which is not generallysuitable for use in the envelope described herein is ordinarypolyethylene, which does not adequately protect the tissue upon thawing.The tissue envelope is easily damaged during freezing, thawing, andshipping, and the tissue may develop cracks upon thawing rendering thetissue unacceptable for transplant purposes.

A three-part test has been developed to select materials which aresuitable for cryogenic packaging. Part A is a general screening testwhereby a sample of the test material is placed into liquid nitrogen(-196 degrees C.) to expose the material to ultracold temperatures. Thematerial is then removed from the liquid nitrogen, and placed into awarm bath until the temperature equilibrates at 37 degrees C. Thissimulates actual treatment conditions during preparation for transplantsurgery.

Part B of the screening procedure utilizes a 100 ml quantity of watercryogenically frozen in an envelope comprised of the test material.After freezing, the package is removed from liquid nitrogen and droppedimmediately from a height of 40 to 45 inches. The package is visuallyinspected for damage to the test material.

Part C of the test is identical to part B, except that the test materialand water contained therein are first cryogenically frozen and thenwarmed to 37° C. The samples are then dropped from a height of 36 to 40inches and examined for damage.

The test results are presented below in table II.

                  TABLE II                                                        ______________________________________                                        RESULTS                                                                       Test Materials      A        B        C                                       ______________________________________                                        Polymide/FEP        3        3        3                                       Foil/Polyester/Polyethylene                                                                       3        1-2      2                                       Teflon (FEP)        2-3      1        2                                       Polyester/Polyethylene                                                                            2        1        2                                       Polyester           2        1        2                                       Matalized Polyester 1        1        1                                       Nylon/Saran         1        1        1                                       Polyethylene        1        1        1                                       ______________________________________                                         LEGEND                                                                        1. Completely unacceptable. Material does not survive the test intact in      least 50% of the trials.                                                      2. Acceptable. This material survives the test in 50% to 90% of the           trials.                                                                       3. Highly Acceptable. This material survived the test in better than 90%      of the trials.                                                           

As will be appreciated from the teachings herein, polyethylene andpolyester are unacceptable from a performance standpoint, due tocracking of the test material and unacceptable levels of tissue damage.In contrast, the polyimide film, for example, demonstrates highlyacceptable physical strength and resistance to the freeze-thaw cycle.Moreover, the polyimide film demonstrates acceptable transplant tissueprotection. One example of a polyimide film useful for the inventiondescribed herein is Kapton®, which is commercially available. Other filmmaterials which meet the above criteria will be equally useful forpracticing the invention described herein. Kapton®'s durability duringthese tests shows a significant and unexpected advantage over all othermaterials tested. This is primarily due to its overall strength andability to remain pliable and flexible at temperatures at least as lowas -196° C. Furthermore, the superior insulating qualities which areexhibited by Kapton® greatly reduce physical damage (i.e. tissuecracking), which occurs during freezing and thawing. Such crackingreduces cellular viability and tissue integrity, rendering the tissueunimplantable. In addition, Kapton® film is chemically inert due in partto a laminated layer of Teflon (FEP).

When fabricating and assembling the envelope package 10, the innermostenvelope 16 is sterile inside and out, and of course the tissue specimen17 and medium 17a sealed within the innermost envelope is also sterile.The interior 26 of the intermediate envelope 14 also are sterilizedbefore receiving the innermost envelope 16, assuring that the innermostenvelope remains in a sterile environment. The outside of theintermediate envelope 14 is likewise sterilized before placing theintermediate envelope within the outermost envelope although, asdiscussed below, the outside of the intermediate envelope is treated asthough non-sterile during subsequent opening of the envelope package 10.

The inside of the outermost envelope 12 is sterilized before theintermediate envelope 14 (containing the innermost envelope 16) isplaced within the outermost envelope. The outermost envelope 12 is thensealed as discussed above, completely isolating the interior of theoutermost envelope from contamination by bacteria or by the liquidnitrogen medium in which the envelope package 10 is subsequently stored.

Once the tissue specimen is fully enclosed within the envelope package10, the packaged tissue is preserved by freezing and is then immersed inliquid nitrogen for preservation.

Opening of the envelope package 10 takes place with the following steps,to preserve the sterility of the innermost envelope 16 and the tissuespecimen 17 contained within the innermost envelope. The entire envelopepackage 10 is removed from the cryogenic storage medium or shippingcontainer (not shown), and is at least partially thawed by placing theenvelope package into a warm water bath. This bath is not sterile butshould be proximate to a sterile field, for example, in the operatingroom where the tissue speciment will be implanted in the recipient. Oncethe envelope package is immersed in the water bath for the desired time,the envelope package is removed and the exterior of the outermostenvelope 12 is dried. The outermost envelope 12 is now opened by cuttingaway the envelope end portion 32, as illustrated in FIG. 3. This cuttingoperation is accomplished with any suitable implement, such as thescalpel 33 or scissors; the involvement preferably is sterile, althoughthis is not a requirement for maintaining the sterility of the tissuesample within the innermost envelope 16.

Once the outermost envelope 12 is cut open, the intermediate envelope 14is withdrawn by using sterile forceps 36 or the like, as illustrated inFIG. 3. Although the interior of the outermost envelope 12 and theexterior of the intermediate envelope 14 were previously sterilized, theexterior of the intermediate envelope is treated as though non-sterilein the opening of the envelope package 10. Thus, it is recognized thatthe outside of the intermediate envelope 14 may become contaminated asthe intermediate envelope is pulled through the cut edge of theoutermost envelope 12, and so removal of the intermediate envelope neednot take place in a sterile field.

The outermost envelope 12 is discarded after the intermediate envelope14 is removed. The peel-back seal 28 of the intermediate envelope 14 isnow opened, using sterilized forceps or other implements to hole thelower layer 24 at the outermost corner 31 while simultaneously unpeelingthe upper layer 25. The completely peeled-back intermediate envelope 14is illustrated at 39 in FIG. 3. The peel-back opening procedure of theintermediate envelope 14 avoids contaminating the interior region 26 ofthe intermediate envelope or the innermost envelope 16 therein,irrespective of possible contamination on the outside of theintermediate envelope. Thus, the upper layer 25 of the intermediateenvelope 14 is peeled back as illustrated at 39 to expose the innermostenvelope 16, without subjecting the innermost envelope to contact withany portion of the outer surface of the intermediate envelope. Theinnermost envelope 16 is now grasped by fresh sterile forceps 37 or thelike, and is removed as indicated at 41 to a sterile field withoutexposing the outside of the innermost envelope to contamination. Theinnermost envelope is then opened in the sterile field, for removal ofthe tissue specimen contained within the innermost envelope.

It will now be understood that the present envelope package maintains atissue specimen isolated from bacterial contamination and from contactwith liquid nitrogen or another storage medium. The outermost envelope12 is made impermeable to liquid nitrogen, without regard to whether theimmediate contents of the outermost envelope become contaminated uponremoval. Even if the intermediate envelope is contaminated when removedfrom the outermost envelope, the intermediate envelope can be opened ina way that preserves sterility of the innermost envelope. Thepossibility of liquid nitrogen seeping through the welds in thepeel-back seal of the intermediate envelope is eliminated, because thepeel-back seal is protected by the nitrogen-impermeable outermostenvelope. Moreover, use of the innermost envelope gives extra sterilityprotection, and sterility of the innermost envelope could be maintainedfor some time even if the outermost envelope ruptures. The resultingenvelope package is more durable than previous packages for steriletissue specimens, and is easier to handle in the hospital operatingroom.

Although preferred materials are disclosed for each envelope, thoseskilled in the art will understand that other materials can besubstituted so long as each individual envelope maintains therequirements disclosed herein. Furthermore, the envelope materials mustbe sterilizable and must withstand cryogenic temperatures withoutundergoing significant degradation of physical qualities.

It should be understood that the foregoing relates only to a preferredembodiment of the present invention, and that numerous changes andmodifications therein may be made without departing from the spirit andscope of the invention as defined in the following claims.

I claim:
 1. A package for storage of a sterile transplantable specimenin a cryogenic atmosphere, comprising:an outermost envelope having anon-sterile exterior that provides an impermeable barrier to thecryogenic atmosphere and having closure means impenetrably sealedagainst the cryogenic atmosphere to define a closed sterile interior, anintermediate envelope removably received within the outer envelope andhaving at least two walls sealed to each other around the peripherythereof to define the closed interior, and an innermost enveloperemovably situated within the interior of the intermediate envelopecomprised of at least two walls sealed to each other around theperiphery thereof to define an inner, sterile cavity, wherein saidoutermost envelope protects against contact by the cryogenic atmosphere,and the intermediate envelope maintains the sterile exterior of theinnermost envelope irrespective of possible contamination occurring tothe exterior of the intermediate envelope during removal from the outerenvelope, said package being in the cryopreserved state.
 2. The packageof claim 1 wherein the outermost envelope is comprised of a materialresistant to damage upon cryopreservation and thawing, and which iseffective for protecting a transplantable tissue sample contained withinthe cavity of the innermost envelope from damage due to cryopreservationand thawing.
 3. The package of claim 2 wherein the outermost envelope iscomprised of polyimide.
 4. The package of claim 3 wherein said polyimideis polyimide/fluorinated ethylene polypropylene laminate.
 5. The packageof claim 1 wherein the innermost envelope is comprised of a materialresistant to damage upon cryopreservation and thawing and which iseffective for protecting a transplantable tissue contained within theinnermost cavity from damage due to cryopreservation and thawing.
 6. Thepackage of claim 5 wherein the innermost envelope is comprised ofpolyimide.
 7. The package of claim 6 wherein said polyimide ispolyimide/fluorinated ethylene polypropylene laminate.
 8. The package ofclaim 1 in combination with a transplantable tissue contained within theinnermost envelope.